From 766ff5a6bd860a53dc72f07196d1a86f29cae8fc Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Tue, 22 Apr 2025 00:05:26 -0700
Subject: [PATCH] Make Fiddle::Pointer#to_str consistent between backends for
 negative pointer sizes

---
 lib/fiddle/ffi_backend.rb   | 3 +++
 test/fiddle/test_pointer.rb | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/lib/fiddle/ffi_backend.rb b/lib/fiddle/ffi_backend.rb
index fc1746fd..f6b3d12f 100644
--- a/lib/fiddle/ffi_backend.rb
+++ b/lib/fiddle/ffi_backend.rb
@@ -432,6 +432,9 @@ def to_str(len = nil)
       if len
         ffi_ptr.read_string(len)
       else
+        if @size < 0
+          raise ArgumentError.new("negative string size (or size too big)")
+        end
         ffi_ptr.read_string(@size)
       end
     rescue FFI::NullPointerError
diff --git a/test/fiddle/test_pointer.rb b/test/fiddle/test_pointer.rb
index 6f086f00..73f163d4 100644
--- a/test/fiddle/test_pointer.rb
+++ b/test/fiddle/test_pointer.rb
@@ -84,6 +84,10 @@ def test_to_str
 
       ptr.size = 0
       assert_equal "", ptr.to_str
+      assert_equal "ello\0", (ptr + 1).to_str(5)
+      assert_raise(ArgumentError) do
+        (ptr + 1).to_str
+      end
     end
 
     def test_to_s
@@ -99,6 +103,8 @@ def test_to_s
 
       ptr.size = 0
       assert_equal "hello", ptr.to_s
+      assert_equal "ello\0", (ptr + 1).to_s(5)
+      assert_equal "ello", (ptr + 1).to_s
     end
 
     def test_minus
@@ -264,6 +270,7 @@ def test_size
       end
       assert_equal 0, Pointer.new(0).size
       assert_equal 0, Pointer.new(0).ref.size
+      assert_equal -1, (Pointer.new(0) + 1).size
     end
 
     def test_size=